bpo-35224: Add PEP 572 (assignment expressions) to What's New

[gvanrossum]

This is a stub, others should elaborate. @emilyemorehouse

https://bugs.python.org/issue35224

[tirkarthi]

It will be great to have this entry since the last alpha for 3.8 is by Monday.

Personal preference : It would be good to have an example with less nesting of parens.

if name := person.get("name"):
    print(f"Hello, {name}")

[gvanrossum]

It will be great to have this entry since the last alpha for 3.8 is by Monday.

I'll try to land it ASAP.

Personal preference : It would be good to have an example with less nesting of parens.

if name := person.get("name"):
    print(f"Hello, {name}")

Hm, I prefer to use parentheses. In practice most examples need them anyway. Also we heard on the bpo issue that people try a := 1 at the REPL prompt and find it doesn't work, then assume it's not implemented yet. An example with parentheses at least gives a little hint towards that.

[tirkarthi]

Hm, I prefer to use parentheses. In practice most examples need them anyway. Also we heard on the bpo issue that people try a := 1 at the REPL prompt and find it doesn't work, then assume it's not implemented yet. An example with parentheses at least gives a little hint towards that.

Makes sense. Thanks 👍

[serhiy-storchaka]

Is this the recommended way of writing such code? Is it more preferable than a separate statement n = len(a)?

[gvanrossum]

Writing it this way indicates to the human reader (though not to the interpreter -- see the PEP's fine print about scopes :-) that n is only relevant inside the if block.

You are really free to write it either way, there is no recommendation intended -- this is just a quick example. (I strongly advise everyone to try and come up with examples that are meaningful, rather than using foo, bar, spam and ham. This one was a compromise. Perhaps someone can come up with a more realistic example where data over (or under!) a certain length must be rejected.

[gvanrossum]

I'm landing this now. @emilyemorehouse please forgive me. See you at PyCon!

[bedevere-bot]

@gvanrossum: Please replace # with GH- in the commit message next time. Thanks!